Trial begins in the case of a 27-year-old off-duty NYPD officer accused of raping a teacher in an upper Manhattan alley last summer.

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An attorney for the off-duty NYPD officer accused of menacing a teacher with his gun and raping her behind an upper Manhattan building last summer acknowledged the assault in his opening statements at trial, but argued his client was innocent because he didn't technically rape the victim.

Lawyer Ephraim Savitt told jurors Michael Pena, who was allegedly drunk during the 20-minute assault on the morning of Aug. 19, "thrust" at the woman multiple times, but was unable to have intercourse with her, according to the Post.

Top New York News Photos of 2011

Savitt described the case as complex.

"This was a terrible crime, an unforgivable crime, but it does not rise to the level of the charges," he said in his opening statement.

Cop Arraigned in Rape Case

Officer Pena gets arraigned (Published Sunday, Aug. 21, 2011)

Prosecutor Evan Krutoy insisted the 27-year-old Pena assaulted the woman in every way imaginable, and argued the DNA evidence, along with witness testimony and the victim's own statement, would prove that, according to the Post.

Authorities said Pena approached the 25-year-old teacher in the early morning after a drunken strip-club binge and asked her how to get to a subway stop. Then they say he grabbed her, ushered her several blocks to an Inwood backyard and raped her.

A neighbor called 911. Pena was arrested after the victim ran to arriving officers and warned them he had a gun.

Pena pleaded not guilty to rape, sex assault and other charges in September. He is currently being held on Rikers Island on $500,000 bail and faces up to life in prison if convicted of the top charges against him.

Pena joined the police force in 2008. He has been suspended without pay.

After Pena was charged, Police Commissioner Raymond Kelly called the allegations "very disturbing" and ordered an investigation into his background to see if there was evidence of other misconduct.

Pena's case is the second rape trial involving NYPD officers in the last year. In May, a jury acquitted Kenneth Moreno and Franklin Mata of raping a woman, but found them guilty of official misconduct, a misdemeanor.

The two were called to help a drunken woman get out of a cab in December 2008.

The woman said she awoke to being raped after passing out. Moreno said he cuddled with her in her bed, but there was no sex. Mata said he was napping on her sofa.

Both officers were fired from the force within hours of the misdemeanor verdict. Moreno was sentenced to a year in jail and Mata received a two-month sentence.

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